Thought to share something that has been very successful in making platform extensions very stiff. Many of my layout designs have have utilized long slender fingers so as to add needed yard facilities while allowing full walk around access.
2', 3' or ?' by 16' +/- peninsulas or other such skinny extensions can be prone to wobble or find themselves to be unreliable for mounting lift out bridges on their ends, plus there can be derailments due to belly bumps.
Over the last few decades I have been using fiber glass Cyclone tension bar "X" members to lock the legs in place. Tension bars are used to tie fence fabric onto corners and ends of chain link fencing.
Granted the same feature can be achieved with lumber but I found these to be visually less intrusive. The can also be used for wall mounted shelf RRs.
3/4" Oak "pillow blocks" fastened on each stud provide a firm mounting attachment. The module is build with 3/4" cross member locations matching the wall stud positions. Twin fiberglass supports ensure balanced compression.
For shelf brackets I use the fiberglass braces in pairs. If they get real long I will use a small piece of 3/4" plywood as a web spacer to steady the rods.
These braces run the East wall of the Cherry Valley Model Railroad club in Merchantville NJ.
Check the OGR calendar and the Cherry Valley website for their winter open house schedule. Pure 0 scale eye candy!
